Piribedil is 2-[1′(3″,4″-methylenedioxy benzyl)-4-piperazinyl]-pyrimidine, and its chemical structure is as follows:

According to the disclosures in U.S. Pat. Nos. 3,299,067 (1967) and 5,362,731 (1994), and Polish patent No. PL 167397 (1995), Piribedil is useful in treating a patient suffering Parkinson's disease or hyperactive bladder, and it can also be used as a peripheral vasodilator, analgesic agent or anti-inflammatory agent.
Polish patent No. PL 167397 (1995) discloses a method of the synthesis of Piribedil comprising reacting 1-(2-pyrimidinyl)piperazine and piperonal in the presence of a reducing agent, formic acid, at a temperature of 100–140° C. The reaction can be represented by the following equation:
This synthesis method is recognized as the simplest method for the preparation of Piribedil. However, the Piribedil product prepared by this method is a light yellow powder having a purity of 98 wt %.
The inventors of the present application have made an approach to purify this Piribedil product including adding this Piribedil product into anhydrous ethanol or 95 wt % ethanol, boiling the resulting mixture, and re-crystallizing. The re-crystallized Piribedil product becomes darker in color and lower in purity. Another approach made is similar to the first approach but further includes a de-coloring step with activated carbon before the re-crystallization. However, the Piribedil purity is not enhanced.
Therefore, there is a need in the industry for a method of the purification of Piribedil, which can increase the purity of the Piribedil product from 98 wt % to a higher purity.